When a human-interface knob is rotated, a sensing mechanism is required to determine properties of the rotation, such as the position of the rotated knob, the direction of rotation and the speed of the rotation. These sensing mechanisms employed by human-interface knobs may be implemented using an incremental rotary encoder that produces electrical signals that describe the properties of the rotation. This sensed information describing the rotation of the knob is then communicated to a logic unit capable of processing this information. Based on this processing, various responses may result depending on the particular system of which the knob is a component. One possible application is a volume knob that can be rotated freely in either direction.
For certain knobs, tactile feedback is desirable since the feedback informs the user of each increment that the knob is turned. In some cases, this feedback may include the use of variable resistance in the rotation of the knob such that certain discrete knob positions are provided for the user, thus improving the ability of the user to accurately and quickly rotate the knob to certain positions. In conventional knobs, tactile feedback is generated mechanically. In conventional mechanical knobs, tactile feedback is implemented using detents, such as interlocking ridges or bent metal, to create a number of stable positions throughout the rotation of the knob. When the knob is rotated, these detents create sectors of high and low resistance in the rotation of the knob. Thus, detents provide tactile feedback during the rotation of the knob and define the discrete positions to which the knob will snap.
These conventional knobs that use mechanical contacts have several disadvantages. Mechanical detents, such as ridges or other structures formed of plastic or metal, wear out with use of the knob. Eventually, all tactile feedback provided by the knob may be lost. In some cases, uneven wear may result in operator error due to inconsistent tactile feedback at different knob positions. The tactile feedback provided using mechanical detents may also be compromised due to corrosion and foreign matter such as dirt impacting the feedback provided by the knob. Creating a system of mechanical detents may also require the generation of complex three-dimensional designs and associated manufacturing processes.